Method and apparatus for coating and drying fabric and other material



Oct. 16 1923. 1,470,650

' P. 5. SMITH FOR COATING AND DRYING FABRIC AND OTHER MAIERIAL Filed y25, 1920 METHOD AND APPARATUS 4 Sheets-Sheet 1 JitvenYor:

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Oct 16,1923. 3 1,470,650

P. 5. SMITH METHOD AND APPARATUS FOR COATING AND DRYING FABRIC AND OTHERMATERIAL Filed May 25 1920 4 Sheets-Sheet 2 Invez1?o2 PM & M

Oct. 1 ,1923. 1,470,650

9. 5. SMITH METHOD AND APPARATUS FOR COATING AND DRYING FABRIC AND OTHENMATERIAL Filed May 25 1920 4 Sheets-Sheet 3 7 new @Mmoo 0 K. (7/ z 4.

Oct. 16 1923. 1,470,650

P. 5. SMITH METHOD AND APPARATUS FOR COATING AND DRYING FABRIC AND'OTHERMATERIAL Filed May 25. 1920 4 snats-sheet 4 Patented Oct. 16, 1923.

. UNITED STATES PATENT OFFICE.

PAUL S. SMITH, OF WEST BARRINGTON, RHODE ISLAND, ASSIGNOR, BY MESNE AS-SIGNMENTS, TO OBANNON COMPANY. OF WEST HARRINGTON, RHODE ISLAND, A

CORPORATION OF MASSACHUSETTS.

METHOD AND APPARATUS FOR COATING AND DRYING FABRIC AND OTHER MATERIAL.

Application filed May 25,

T all whom it may concern:

Be it known that'I, PAUL S. SMITH, a citizen of the United States,residing at West Barrington, in the county of Bristol and State of RhodeIsland, have invented an Improvement in Methods and Apparatus forCoating and Dryin Fabric and Other Material, of which the iollowing is aspecification.

This invention relates to the coatingand drying of material in the webfor the production of so-called artificial leather and the like, and therecovery of solvents from the coating, and has for its object to dry thecoating and recover the highly inflammable readily vaporizable solventtherefrom and prevent the formation of an explosive mixture of thesolvent and drying medium in the drying chamber of the coatingapparatus.

However, this invention is not designed to prevent fire, due to ignitionof the wet coating, as contrasted with the explosion of the gaseousmixture of solvent vapor and drying medium.

There are many types of apparatus for the recovery of solvent from thecoating, wherein a minimum of drying medium, as air is employed which iscaused to absorb a relatively large amount of solvent vapor so andthereby become explosive; or wherein a relatively large amount of air isused which is given such a slow movement as to absorb a relatively largeamount of solvent vappr, and becomes explosive.

as y method of preventing explosions consists enerically in preventingthe formation in the dryin chamber of a mixture rich enough in so ventvapor to be explosive at any stage of the drying process.

In carrylng out my invention I employ a relatively small volume of airat subnormal humidity and circulate it through my apparatus at such arelatively high speed that the proportion of solvent vapor absorbed eathereby is too small to form an explosive mixture. Furthermore, I coolthe air by artificial cooling means, to a relatively low temperature sothat the air returned to the drying chamber is exceedingly dry and rela-50 tively cold. Heating means are arranged in the drying chamber, mainlyto compensate 1920. Seria1 No. 384,228.

.for the cooling efi'ect of the solvent absorption, by which the humidsolvent leaves the drying chamber but relatively slightly increased intemperature. The maintenance of a relatively low temperature aidsgreatly in reducing the possibility of formation of a mixture richenough to explode. Both the speed of the air through the apparatus, andthe temperature of the air, are regulated whereby any desired degree ofsaturation of the d ing medium with solvent vapor may be maintained andthe mixture kept below the explosive point.

My process may be used in any recovery apparatus which is notparticularly designed to act differently, as, for instance, myco-pending application Serial No. 369,- 823, filed March 29, 1920, butnot apparatus like May and Grosvenor, Patent No. 979,- 781, datedDecember 27, 1910, in which a large, Slow movin body of air is usedwhich necessarily becomes explosive, as is recognized in said patent bythe provision of explosion doors which are arranged automatically toopen to diminish the. harmful effect of the inevitable explosion.

Fig. 1 is a side elevation of a drying and recovery apparatus welladapted for the performance of my invention.

Fig. 2 is a diagrammatic sectional elevation of the apparatus. of Fig.1.

Fig. 3 is a partial sectional plan View of the drying chamber alonglines 3--3 of Fig. 1 showing air heating 0011s and dry air distributionpipes.

Fig. 4 is a detail, in transverse sectional elevation, of the dryingchamber of Fig. 1.

Fig. 5 is a sectional plan view of the solvent separator along lines 55of Fig. 1.

Figs. 6 and 7 are details in elevation and plan, respectively, of loopforming mechanism.

In the dr ing and solvent recovery apparatus here s own, which is welladapted for the recovery of solvent and prevention of the formation ofan explosive mixture in accordance with my invention, the drying chamberis divided by partitions to form four different drying compartments 10,11, 'mo 12, 13, on difierent levels, with connectin passages 14., 15,16, through which the we passes under tension from the upper to the nextlower compartment around a guide roll until the solvent hassubstantially evaporated.

The drying medium passes in the contrary direction, preferably first tothe lower compartment and then contrary to the movement of'the web tothe upper compartments ofthe drying chamber. After the drylng medlum haspassed to the top compartment of the drying chamber, it passes out ofthe drying chamber at a point near the entrance of the web and thencethrough condensing apparatus for the recovery of the solvent.

The lower compartment 13 of the drying chamber forms what may be termeda loop chamber in which the coated and partially dried web, as it passesfrom the upper compartments is arranged in 100 s on a conveyor andcarried to the exit rom the drying chamber. Heating coils 17 are placedin said chamber and are adapted suitably to heat the air in the chamberto compensate for the reduction in temperature of the dryinglmedium dueto solvent absorption.

eating coils 18 are placed at the top of the compartment 12 alsosuitably to heat the air therein.

The upper'wall 19 of said compartment 12 forms the lower wall ofcompartment 11 and is made of metal or other good conductor. Accordinglysaid compartment 11, owing to the close proximity of the heating coils18 in the lower compartment, receives a considerable amount of heat fromsaid heating coils. The upper compartment 10 I usually have free fromartificial heating means, yet heating means may be introduced therein ifdesirable.

Nevertheless, the air in this upper chamber should not be allowed tobecome so cold as to interfere with the process of evapora tion, and incase the evaporation cools the air in this upper chamber unduly, amoderate heat should be supplied to maintain the drying medium at asuitable temperature.

I prefer to make the top compartment 10 shallower than the compartments11 and 12 as there is a greater amount of solvent in the coating in saidtop compartment with the result that the velocity of the air therein isgreater than in the lower compartments and the drying medium will absorbless solvent vapor.

The web may be passed as a continuous loop a successive number of timesthrough the apparatus to receive and dry a succesfsive number hfcoatings thereon, or the web may be passed but once through theapparatus and, with a single coating thereon, formed in a roll. 1

As here shown, the web 20 in the form of a roll is arran'gedon ahorizontal shaft 21 journalled in suitable bearings secured to the frameof the drying chamber. Said shaft isprovided with a brake drum 22 whichis adapted to be engaged by a brake band 23 to adjust the tension of theweb a or compartment 10 of the drying chamber.

The coated web is extended under tension through said compartment andpassed over an upper driving roll 28 disposed in the connecting passage14 between the upper compartment 10 and the next lower compartment 11and extended through said lower compartment and passed around a guideroll 29 disposed in the connecting passage 15 between said compartment11 and the next lower compartment 12. After leaving said guide roll 29the web is extended under tension through said compartment 12 and passedover the lower driving roll 30 disposed in the passage 16 connectingsaid compartment 12 with the loop chamber 13. From said driving roll 30the web is passed around a nip roll 31 disposed in the loop compartment13 from which it falls by gravity onto a conveyor arranged in saidcompartment and by which it is carried to the exit from the dryingchamber.

After passing through the exit slot 32 in the drying chamber the web isextended over the guide rolls 33 and 34 and around the tension drum 35and over the roll 24 to the doctor to receive another coating. After theweb has received a sufiicient number of coatings the ends of the webmaybe separated, preferably between the rolls 33 and 34, and formed in aroll on the shaft 36.

The power for driving the various rolls to move the web through themachine is applied at a pulley 37 fixed to a shaft 37' convenientlydisposed at the top of the drying chamber. A gear 39 secured to saidshaft is in mesh with a gear 39 fixed to the shaft carrying the upperweb driving roll 28 and serves to drive said roll at such speed as tocause the most efi'ective movement of the web through the dryingchamber.

The shaft carrying roll 28 is also provided with a pulley 40, and a belt41 is passed over said pulley and a pulley 42 of slightly smallerdiameter secured to the shaft bearing the lower web driving roll 30whereby the lower drying roll maintains a suitable tension on the web. Abelt tightener 43 is or may be arranged in contact with said belt tomaintain it in proper driving fiontact with the pulleys.

e roll 31, over which the web Passes vertical shaft 53.

from roll 30, is driven from the shaft bearing the roll 30 by themeshing gears 44 and 45. Said roll 31 is adapted to be driven at aslightly greater peripheral speed than the web driving rolls to aid inkeeping a taut web extended through the upper drying compartments.

From roll 31 the web falls by its weight onto a conveyor where it isarranged in loops thereon and conveyed to the exit end of the dryingchamber.

The conveyor includes two spaced-apart endless chains 46 and 46connected at regular intervals by the cross-bars 47 on which the loopsof web are adapted to be hung. Said chains are arranged over sprockets48 and 48", 49 and 49*, 50 and50, 51 and 5l disposed at the corners ofthe loop chamber 13.

The conve or is driven by the sprockets 50 and 50 w ich are driven fromthe shaft bearing the roll 28 through the horizontal shaft 59 andvertical shaft 53 which are operablv connected through gears with saidroll shaft.

Change speed gearing is interposed between the shaft 53 and thesprockets'50 and 50 whereby more than a single speed of the conveyor maybe obtained, whereby diden ent lengths of coated web may be made tooccupy substantially the entire length of the chamber.

As here shown, gear 54 and 54 of said gearing are fixed to a shaft 55driven through bevel gears 56 and 56"- i'rom the Other gears 57 and 58of said change speed gearing are fixed togather or are integrally formedand are slidably arranged on a shaft 59 which is oonnected though a worm60 and gear 61 to the shaft carrying sprockets 50 and 50*. A pivotedhandle 62 is provided which is in engagement witli'said sliding gears 57and 58 to cause said gear 57 to engage with the gear 54, or gear 58 toengage with gear 54*, and said pairs of gears are arranged to drive saidsprockets 50 and 50" at differing speeds to correspondingly drive theconveyor at differing speeds.

Said vertical shaft is extended downward beyond its connection with thejchangc speed shaft 55 and, at its lower end. is connected with a shaft63 through which the roll of web is driven and wound on shaft 36.

As the web passes from the roll 31 it is arranged to fall downward andpass between the cross-bars 47 of the conveyor and, as the conveyor isat the same time moved forward, to form loops on said cross-bars.

In order that the loops may be more efiectively and positively formed,means are provided for definitely folding the web over the cross-bars asthey are successively moved under the roll 31.

The loop forming means includes rods 65 and 65 which are pivoted tobeams 66 and 66 arranged at the sides of'the conveyor and secured tocomponent parts of the drying chamber. Said rods extend downward intothe path of movement of the cross-bars of the conveyor and are adaptedto be moved upward by the individual bars as they pass under said rodsand to permit said rods to drgp by gravity as they pass from under there s.

Said rods are provided, near their free ends, with outwardly extendedmembers 67 and 67 in the ends of which is arranged the cross-member 68which extends above and across the conveyor and which is adapted to bebrought into contact with the web to form the loops.

Other rods 70 and 7 0", bent into substantially right-angled shape, arepivoted to said beams 66 and 66 at points adjacent to and above theconveyor, and a rod 71 is extended between and connected to the freeends thereof.

As the ends of rods 65 and 65*- are moved upward by each cross-bar 47 asit passes underneath, the cross-rod 68 connected to said rods enga%s'therods 70 and moves them upward t ereby also moving upward the rod 71connected to the ends thereof.

When the cross-bars pass from under said rods 65 and (55" the rodsrapidly drop by gravity and consequently permit the rods 70 and 70bearing the cross-rod 71 to drop. As said rod 71 falls it strikesagainst the web which passes in a more or less downwardly slantingdirection from the roll 31 to a cross bar 47 inthe rear of the oneemployed in raising the rods 65 and 65, and by its weight and momentumbends or folds the web over said cross-bar and so initiates theformation of a loop between said crossbar and the next succeeding one.The same operation is repeated as each cross-bar passes under the rods65 and 65*.

A blower or compressor 80 of any suitable or desirable construction isemployed to ensure a positive circulation of the drying medium throughthe drying chamber and the condensing system and solvent bearing air isdrawn from the top compartment 10 of the drying chamber through theconduit 7 5 into the intake end of the blower or compressor. A pipe 81also leads from the hood 26 to the compressor intake to collect thevaporized solvent in the hood. From the blower or compressor the solventbearing air is forced through the cooling and condensing apparatus.

Although I have shown the blower or com pressor as connected between thedrying Ill) chamber and the condensing apparatus, yet

An important feature of my invention is the control ofthe speedofcirculation of the drying medium by which the absorption of the solventmay be regulated and the formation of a mixture of the drying medium andvaporized solvent rich enough in solvent vapor to explode prevented.

As a convenient means for controlling the circulation of the dryingmedium, I govern the speed of the blower 80. Said blower has a ulley 80'fixed to the blower shaft over which a driving belt 80 is passed. Saidbelt is also passed over the pulley 80 which supplies the. power tooperate the blower. A controller 80 arranged in the motor circuit 80provides means by which the rate of rotation of the motor may begoverned at will and consequently the rate of circulation of the dryingmedium through the apparatus will be governed. Obviously, however, othermeans of blower-driving and air circulation control may be provided.

I prefer to pass the warm air from the drying chamber through a heatexchanging.

device through which the air from which the solvent has been extractedis passed in the reverse direction before being returned to the dryingchamber.

I also prefer to pass the .air from which the solvent has been condensedand before it has been reheated through a mechanical separator which mayhave a series of baflleplates or similar collecting devices as I havefound that the air from the condenser even when chilled contains aconsiderable amount of condensed solvent in the form of 'fine spraywhich, if not removed, would be returned to the drying chamber andrender the returned air less effective as a drying and absorbing medium.

The condensing system includes a precooler 85, heat exchangers. 86, 8686", and condensers 87, 87*, 87 through which the air is successivelyforced through the pipe 88 from the blower 80. The pre-cooler,heatexchangers and condensers may be of any ordinary or suitableconstruction and as many units as are desirable may be employed.

In the pre-cooler 85 water is introduced at the bottom of the shellthrough the pipe 89 and flows upward in a direction contrary to thedownward flow of solvent laden air therethrough and leaves the shell bthe pipe 90. In its passage therethrouih the water absorbs some of theheat of t e air and causes the air to become more nearly saturated withthe absorbed solvent.

The somewhat cooled air passes from the pre-cooler successively throughthe heat exchangers 86, 86, 86". The cold dry air from the condensers iscirculated through the shells of said heat exchangers in a directioncontrary to the flowof moist air therethrough and serves to extractheat. from of the drying chamber.

said moist air and to become somewhat heated in itself and in its heatedcondition passes by the pipe 78 to the loop compartments 13 The moistair, as it leaves the heat exchangers, is cool and in a more or lesssaturated condition and enters the condensers 87 87, 87" through whichit successively passes. The condensers are maintained cold by means of asolution of brine or other suitable refrigerating medium supplied to theshell of the condensers through the pipe 91 and flowing from saidcondensers in a partially heated condition through the pipe 92, havingextracted heat from the drying medium in its passage therethrough. Thebrine of other refri rant ma be cooled by any suitable artlfi'cial .cooing means. Preferably the temperature of the brine is such that thetemperature of the dry air is relatively low, say about 0F., when itleaves the condensers.

'As the air passes through the condensing units it becomes successivelycooler and the evaporated solvent absorbed therein becomes condensed andseparates from the air and collects at the bottom of the condensingunits or at the bend in the pipes serially connectin the units.Connections are made with the ower arts of the units and 95 for therecovery 0 the condensed solvent.

After passing from. the. last condensi unit 87 the major part of theabsorb dd solvent has been condensed and recovered yet the cold aircontains a substantial amount of mechanically entrained solvent in theform of a fine spray.

A mechanical separator is inserted in the pipe for the cooled air as itpasses from the last condensing unit 87* to extract this remainingmoisture. The separator is provided with a plurality of bathe-plates 101or equivalent devices arranged in the path of flow of the cold air whichserve to abstract the moisture from the air as it impinges thereon andto collect it in the receiver 102 from which it flows through the pipe103 to-the solvent pipe 95.

The cold and dry air is now directed through the heat exchangers whereits temperature is raised in lowering the temperature of the moist airand: passes through the pipe 78 to the bottom of the loop chamber 13 inwhich it is uniformly distributed by the plurality of perforateddistributing pipe 105 placed therein over the heating coils .17. 1

A further important feature of this invention is the control of thetemperature of the dry drying medium, by the maintenance of 'a lowtemperature for it, a relatively lean and therefore unexplosive mixture.results especially when used in combination with the regulation of the.rate of circulation of the drying medium. For this purpose, a regulatingvalve 91is arranged in the brine pipe 91 by which the rate ofcirculation of the cold brine or other refrigerating medium may beregulated thereby to vary the rate of cooling, and the finaltemperature, for the drying medium in the condensers.

A thermometer 92 placed in the pipe which serves to direct the cold drydrying medium to the heat exchangers and thence to the drying chamberwill indicate the temerature of the dry drying medium, whereby properregulation of the cooling effect ma conveniently be efiected.

will be noted that the drying sections of the drying chamber, with theexception of the loop compartment, are restricted in vertical extent sothat the drying medium flows therethrough at a relatively rapid rate,which is desirable, as it assists in preventing the formation of mixturerich enough in solvent vapor to explode.

While it is possible to maintain the mixture of solvent vapor and dryingmedium at a point below that at which explosions will occur, byregulation of velocity of flow of drying medium alone, or by temperaturecontrol alone, yet I prefer to govern both the temperature and speed ofthe dry ing mixture as productive of more satisfactory results.

With a fixed rate of input of solvent into the drying chamber, as by afixed speed of the wet coated web through the chamber, a certain speedof drying medium and temperature of drying medium will result for theperformance of the invention.

An appreciable variation of the rate of input of solvent, as by varyingthe speed of the material through the drying chamher, or varying thethickness of the coatingap lied thereto, or varying the proportion 0solvent therein, may necessitate variation of temperature and speed ofthe drying medium in the drying chamber. Ordinarily, however, thesubstitution of one solvent for another, so far as the common solvents,as benzol, ethyl acetate, wood alcohol and the like are concerned, Willnot necessitate varying the speed or temperature of the drying medium inthe drying chamber.

Usually, and as herein shown, the speed of the Wet material through thedrying chamber will be fixed at some predetermined value, and the speedof the drying medium through the chamber, and its temperature, when oncedetermined, usually need not be changed; so that with the speed of theweb, and the cross-section of the passages in the drying chamber known,the capacity and speed of rotation of the blower, and the temperature ofthe drying medium, may bepredetermined in advance, so that no speed ortemperature adjustments need be made for the commercial operation of theap aratus.

p y invention relates only to the treatment of coating mixturescontaining a solvent, the vapor of which becomes explosive when mixedwith certain proportions of air, and the specification and claims shouldbe read with that understanding.

In case, in a coating apparatus, a moist air is supplied to the dryingchambers and permitted to condense on the goods, the coating materialmay be precipitated, causing a defect in the product, called blushing.This danger I avoid by reason of the fact that the moisture is socompletely condensed from the drying medium before the drying mediumisreturned to the apparatus that no Water vapor will be condensed at anytemperature reached in the drying process.

l'claimz- 1. The method of recovering the solvent from the coating offabrics such solvent consisting of a mixture containing a highlyvolatile solvent the vapor of which is explosive when mixed with acritical proporrent of drying medium in a drying chamber counter to thedirection of movement of the moving coated fabric in the chamber untilthe fabric is dry, at such a speed that the proportion of explosivesolvent vapor in the drying medium is not great enough to form anexplosive mixture, removing the drying medium containing the solvent toa condensing apparatus and condensing the solvent by refrigeration andagain passing the drying medium from which the solvent has beenrecovered into contact with the coated fabric.

2. The method of recovering the solvent from the coating of fabrics suchsolvent consisting of a mixture containing a highly volatile solvent thevapor of which is explosive when mixed with a critical proportion ofair, which consists in passing a current of drying medium in a dryingchamber counter to the direction ofmovement of the moving coated fabricin the chamber until the fabric is dry, at such speed that theproportion of explosive solvent vapor in the drying medium is not greatenough to form'an explosive mixture, removing the drying mediumcontaining the solvent to a condensing apparatus and condensing thesolvent by refrigeration and again passing the drying medium from whichthe solvent has been recovered into contact with the coated fabric andmaintaining the temperature of the drying medium while in contact withthe coated fabric at a suitable value.

3. The method of recovering the solvent from the coating of fabrics suchsolvent consisting of a mixture containing a highly Hill) volatilesolvent the vapor of which is explosive when mixed with a criticalproportion of air, which consists in passing a current of drying mediumin a drying chamber counter to the direction of movement of the movingcoated fabric in the chamber until the fabric is dry, at such speed andtemperature that the proportion of explosive solvent vapor .in thedrying medium is not great enough to form an explosive mixture, removingthe drying medium containing the solvent to a condensing apparatus andcondensing the solvent by refrigeration and again passing the dryingmedium from which the solvent has been recovered into contact with thecoated fabric.

4. The method of recovering the solvent from the coating of fabrics suchsolvent consisting of a mixture containing a highly volatile solvent thevapor of which is explosive when mixed with a critical proportion ofair, which consists in passing a cur rent of drying medium in a dryingchamber counter to the direction of movement of the moving coated fabricin the chamber until the fabric is dry, at such speed and temperaturethat the proportion of explosive solvent vapor in the drying medium isnot great enough to form an explosive mixture, removing the dryingmedium containing the solvent to a condensing apparatus and condensingthe solvent by refrigeration and again passing the drying medium fromwhich the solvent has been recovered into contact with the coated fabricand maintaining the temperature of the drying medium while in contactwith the coated fabric at a suitable value.

5. In a coating apparatus for material in the web, including a dryingchamber through which the wet coated material is moved to be dried, andsolvent recovery apparatus in which the drying medium is cooled andsolvent condensed, means to circulate the drying medium through thedrying chamber to abstract solvent from the material therein and thencethrough the solvent recovery apparatus to extract solvent therefrom andback to the drying chamber with solvent extracted therefrom, and meansto maintain the proportion of solvent vapor in the drying medium in thedrying chamber below that at which a mixture of the solvent vapor anddrying medium will explode.

6. In a coating apparatus for materialin the web, including a dryingchamber through which the wet coated material is moved to be dried, andsolvent recovery apparatus in which the drying medium is cooled andsolvent condensed, means to circulate the drying medium through thedrying chamber to abstract solvent from the material therein and thencethrough the solvent recovery apparatus to extract solchamber withsolvent extracted therefrom and means to, maintain the proportion ofsolvent vapor in the drying medium in the drying chamber below thatproportion at which a mixture of the solvent vapor and drying mediumwill explode comprising means to govern the rate of circulation ofdrying medium in the drying chamber.

7 In a coating apparatus for material in the web, including a dryingchamber through which the wet coated material is moved to be dried, andsolvent recovery apparatus in which the drying medium is cooled andsolvent condensed, means to circulate the drying medium through thedrying chamber to abstract solvent from the material therein and thencethrough the solvent recovery apparatus to extract solvent therefrom andback to the dryin chamber in cold and dry condition, and means tomaintain the proportion of solvent vapor in the drying medium in thedrying chamber below that proportion at which a mixture of the solventvapor and drying medium will explode, comprising means to govern thetemperature of the drying medium in the drying chamber.

8. In a coating apparatus for material in the web, including a dryingchamber through which the wet coated material is moved to be dried, andsolvent recovery apparatus in which the drying medium is cooled andsolvent condensed, means to circulate the drying medium through thedrying chamber to abstract solvent from the material therein and thencethrough the solvent recovery apparatus to extract solvent therefrom andback to the drying chamber in cold and dry condition, and means tomaintain the proportion of solvent vapor in the drying medium in thedrying chamber below that proportion at which a mixture of the solventvapor and drying medium will explode comprising means to maintain areduced temperature of the drying medium in the drying chamber.

9. In a coating apparatus'for material in the web, including a dryingchamber through which the wet coated material is moved to be dried, andsolvent recovery apparatus in which the drying medium is cooled andsolvent condensed, means to circulate the drying medium through thedrying chamber to abstract solvent from the material thereinand thencethrough the solvent recovery apparatus to extract solvent therefrom andback to the drying chamber in cold and dry condition, and means tomaintain the proportion of solvent vapor in the drying medium in thedrying chamber below that proportion at which a mixture of the dryingchamber, and means to govern the temperature of the drying medium in thed ing chamber.

10. n a coating apparatus for material in the web, including a dryingchamber through which the wet coated web is moved arranged to guide acurrent of drying medium over the web counter to the direction ofmovement of the web, means to prevent explosion of the mixture ofsolvent vapor and drying medium therein comprislng means to circulatethe drying medium through the drying chamber at such a rapid rate as torevent the formation of a mixture of sol i'ent vapor and drying mediumrich enough in solvent vapor to explode.

11. In a coating apparatus for material in the web, including a dryinchamber through which the wet coated we is moved arranged to guide acurrent of drying medium over the web in a direction counter to themovement of the web in the chamber, a

solvent recovery apparatus in which the dryin medium is.cooled andsolventcondense means tocirculate the drying medium through the dryingchamber to ab-. stract solvent from the wet coati thence through therecovery apparatus an back to the drying chamber in cold and drycondition, means to prevent explosion of the mixture of solvent va r anddrying medium in the drying cham r comprising means to maintain areduced temperature of the drying medium in the drying chamber of such avalue as to prevent the formation of a mixture rich enough in solventvapor to *'explode.

12. In a coating apparatus for material in the web-,including a dryingchamber through which the wet coated web is moved arranged to guide acurrent of drying medium over the web in a direction counter to themovement of the web in the chamber, a solvent recovery apparatus inwhich the drying medium is cooled and solvent condensed, means tocirculate the drying medium through the drying chamber to abstractsolvent from the wet coating, thence through the recovery 'apvparatusand back to the drying chamber in cold'and d condition, means to preventexplosion of t e mixture of solvent vapor and drying medium in the dryinchamber com rising means to circulate t e drying medium through thedrying chamber at such a rapid rate, and other means to maintaina'reduced temperature of the dr ing medium in the drying chamber of suea value, as to prevent the formation of a mixture rich enough in solventvapor to explode.

13. In a coating apparatus for material in the web, including a coatingdevice, a drying chamber having restricted passages through which thewet coated web is moved to be dried, solvent recovery apparatus in whichthe dryin medium is cooled and solvent condense means to circulate thedrying medium rapidly through the restricted passages in the dryingchamber in a direction counter to the movement of the material thereinto abstract solvent from the coating, thence through the recoveryapparates for cooling and extraction of solvent, and back to the dryingchamber in cold and dry condition, and means to prevent explosions ofthe mixture of solvent vapor and drying medium in the drying chambercomrising the combination of means so to reguate the speed of the dryingmedium through the drying chamber, and other means so to govern thetemperature of the drying meium in the drying chamber as to prevent theformation of a mixture rich enough in solvent vapor to explode.

In testimony whereof I have signed my name to this specification.

PAUL S. SMITH.

